Search Images Maps Play YouTube News Gmail Drive More »
Sign in
Screen reader users: click this link for accessible mode. Accessible mode has the same essential features but works better with your reader.

Patents

  1. Advanced Patent Search
Publication numberUS4859827 A
Publication typeGrant
Application numberUS 07/259,024
Publication dateAug 22, 1989
Filing dateOct 17, 1988
Priority dateOct 17, 1988
Fee statusPaid
Also published asCA1324820C, DE68925262D1, DE68925262T2, EP0365180A2, EP0365180A3, EP0365180B1
Publication number07259024, 259024, US 4859827 A, US 4859827A, US-A-4859827, US4859827 A, US4859827A
InventorsRichard J. Coyle, Jr., Jaroslav Mracek
Original AssigneeAmerican Telephone And Telegraph Company
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Method for welding relatively small parts
US 4859827 A
Abstract
Laser welding of an outer sleeve 14 to an inner fiber ferrule 12 is expedited by, first, machining a thinned region 18 in the outer diameter of the sleeve. After the ferrule has been inserted in the sleeve, the thinned region permits the laser to fuse through the sleeve and melt part of the ferrule, as is required for laser welding of ferrule for the sleeve. The thinned region is preferably made by using a rotary cutter to cut an axially extending slot in the outer sleeve, which permits a succession of laser welds 21 in the axial direction in the slot. In a preferred embodiment, thinned regions 18,19 are made on opposite sides of the outer sleeve, and laser welding is performed simultaneously on both sides of the sleeve so as to avoid distortions caused by thermal stress asymmetries.
Images(1)
Previous page
Next page
Claims(10)
We claim:
1. A method for assembling optical apparatus comprising the steps of: mounting an optical fiber ferrule within a metal sleeve; orienting the ferrule within the sleeve to attain a desired orientation of the optical fiber with respect to the sleeve; and using a laser beam to weld permanently the ferrule to the sleeve, characterized in that:
prior to the mounting, a portion of the sleeve is made significantly thinner than the remainder of the sleeve; and the welding step comprises the step of directing the laser beam at the thinned portion of the sleeve.
2. The method of claim 1 further characterized in that:
the step of making a portion of the sleeve significantly thinner comprises the step of using a rotary cutter to cut at least one slot in the metal sleeve.
3. The method of claim 1 further characterized in that:
prior to the mounting, two diametrically opposite portions of the sleeve are made thinner than the remainder of the sleeve; and the welding step comprises the step of simultaneously directing laser beams at both thinned portions of the sleeve.
4. The method of claim 3 further characterized in that:
in each of the opposite thinned portion of the sleeve, a plurality of welds are made along a line substantially parallel to the sleeve.
5. The method of claim 4 further characterized in that:
a rotary cutter is used to cut the sleeve to make each of the two thinned portions; and during such cutting operation, the rotary cutter has a plane that is parallel to the center axis of the sleeve.
6. A method for laser welding a first relatively small element to a second relatively small element characterized by the steps of:
machining a portion of the second element so as to make such portion thinner than the remaining part of the second element; overlapping the thinned portion of the second element over the first element; and using a laser beam to melt through the second element and to melt part of the first element so as to cause fusion between the first and second elements.
7. The method of claim 6 further characterized in that: the first element has a cylindrical outer surface;
and the second element is an outer sleeve that contains snugly the first element.
8. The method of claim 7 further characterized in that: the thinned portion of the outer sleeve is made by cutting an axially extending slot in the outer sleeve, the slot extending through only a portion of the thickness of the outer sleeve.
9. The method of claim 8 further characterized in that:
slots are made on diametrically opposite sides of the sleeve; and the welding step comprises a step of simultaneously directing laser beams at both thinned portions of the sleeve.
10. The method of claim 9 further characterized in that:
in each slot a plurality of welds are made along a line substantially parallel to the axis of the sleeve.
Description
TECHNICAL FIELD

This invention relates to methods for welding relatively small parts and, more particularly, to methods for welding an outer sleeve to an optical fiber ferrule.

BACKGROUND OF THE INVENTION

Recent advances in lasers, optical components and optical fibers for transmitting information in the form of lightwaves have led to proposals for generalized lightwave communications systems. The proposed use of lightwave communication as a general alternative to telephone communications presupposes an ability to make small optical components in great volume and with great precision. One basic component for such systems would be the optical coupler for transfering information to an optical fiber and removing information from the optical fiber, as is described, for example, in the patent of DiDomenico et al. U.S. Pat. No. 4,165,496, granted Aug. 21, 1979, and assigned to Bell Telephone Laboratories, Inc. The assembly of such an optical coupler requires proper alignment and positioning of two abutting optical fibers.

Positioning of a small diameter optical fiber with respect to an optical coupler is now typically done by mounting the optical fiber in a ferrule. The ferrule is snugly fitted within a sleeve which is moved axailly to a proper position and then the ferrule is bonded to the outer sleeve. Thereafter, the sleeve is fixed to the coupler and is rotated to give the optical fiber a proper angular alignment with respect to the coupler.

Optical fiber is normally bonded within the ferrule by an epoxy, which has been found to be satisfactory. It is, however, difficult to bond the ferrule to the outer sleeve after the required axial adjustment has been made. Laser welding is the most practical method for such bonding, but it poses problems because it is not practical to use it to fuse through the entire thickness of the outer sleeve. Such welding would require undesirably high laser power, and the concomitant heat would tend to distort the elements. Thus, attempts have been made to laser bond at the interface between the sleeve and the ferrule, which is difficult because of the accurate placement of the laser beam that is required. There is, therefore, a need for a method for welding the relatively small sleeve to the optical fiber ferrule in a manner that is readily amenable to mass production.

SUMMARY OF THE INVENTION

In accordance with the invention, laser welding of an outer sleeve to an inner fiber ferrule is greatly expedited by, first, machining a thinned region in the outer diameter of the sleeve. After the ferrule has been inserted into the sleeve, the thinned region permits the laser to fuse through the sleeve and melt part of the ferrule, as is required for laser welding of the ferrule to the sleeve. As will be discussed in more detail later, the thinned region is preferably made by using a rotary cutter to cut an axially extending slot in the outer sleeve that does not extend through the entire outer sleeve. This permits a succession of laser welds in an axial direction in the slot to give dependable fusion between the ferrule and the outer sleeve. In a preferred embodiment, thinned regions are made on opposite sides of the outer sleeve and laser welding is performed simultaneously on both sides of the sleeve so as to avoid distortions caused by thermal stress asymmetries.

These and other objects, features, and advantages will be better understood from a consideration of the following detailed description taken in conjunction with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a sectional view illustrating a method for laser welding an outer sleeve to a fiber ferrule;

FIG. 2 is a sectional view illustrating a method for laser welding an outer sleeve to a fiber ferrule in accordance with an illustrative embodiment of the invention;

FIG. 3 is a top view of the assembly of FIG. 2.

DETAILED DESCRIPTION

Referring now to FIG. 1, there is shown an optical fiber 11 mounted within a cylindrical ferrule 12. The ferrule 12 is used to permit the fiber to be attached to other elements and is typically securely bonded to the fiber with an epoxy adhesive. For the fiber to be mounted in an optical coupler, it is typically necessary to slidably mount the ferrule 12 within a metal sleeve 14. The sleeve 14 is then mounted to the coupler (not shown).

Such mounting in the coupler normally requires that the fiber be positioned or aligned properly in both the axial and the rotational directions. This can best be done by first sliding the fiber ferrule axially to a proper position within the sleeve 14 and then permanently bonding the sleeve 14 and the ferrule 12. Thereafter, the sleeve, ferrule and fiber can be rotated as a unit for proper rotational alignment. It has been found that, after axial alignment, the best method for bonding the sleeve to the ferrule is by laser welding. As described in the patent of Cruickshank et al., U.S. Pat. No. 4,733,047, granted Mar. 22, 1988, and assigned to the American Telephone and Telegraph Company, which is incorporated herein by reference, laser welding of small parts that have to be maintained in proper alignment is best done by splitting the laser beam and delivering it by two optical fibers so as to permit simultaneous welding on opposite sides of the article. In FIG. 1 laser welds 15 and 16 are simultaneously made by two laser beams delivered from a common pulsed laser.

A major problem we have encountered in making the assembly shown in FIG. 1 is the difficulty of making welds 15 and 16 so that they reliably fuse together the sleeve 14 and ferrule 12. Any slight misalignment of the laser beam will cause inadequate melting of either the sleeve or the ferrule. It is not practical to fuse through the entire thickness of sleeve 14 because the heat and power required for such operation would distort the alignment of the various elements.

Referring to FIG. 2, in accordance with one embodiment of the invention, these problems are solved by forming thinned regions 18 and 19 on opposite sides of the annular sleeve 14. This makes it possible to form laser welds 21 and 22 on opposite sides of sleeve 14, which dependably extend through the sleeve to fuse portions of ferrule 12, as required for bonding the ferrule to the sleeve. As in FIG. 1, each of the welds 21 is made simultaneously with a weld 22 on the opposite side of the sleeve. This is preferably done by using the laser beam transmission system described in the aforementioned Cruickshank et al. patent for making simultaneous welds that produce thermal stresses that are symmetrical and thereby less likely to deform the elements. The laser beams are taken from a single laser and delivered via optical fibers 23 to the weld sites. With the thinning of the outer sleeve and with simultaneous welding in this manner, we have found that welds 21 and 22 dependably can be made with a sufficiently low power laser beam to avoid harmful thermal stresses on the elements. Further, the laser beams do not damage the fiber 11 or vaporize the epoxy adhesive, which would also be harmful to the light transmission properties of the fiber. A top view of the FIG. 2 assembly is shown in FIG. 3 which shows the three laser welds 21 within thinned portion 18.

All of the elements of FIG. 2 are dimensionally quite small: optical fiber 11 may have a diameter of 0.04 inch; the outer diameter of ferrule 12 may be 0.120 inch; the outer diameter of sleeve 14 may be 0.170 inch; the axial length of sleeve 14 may be 0.286 inch. Welds 21 and 22 may have center-to-center spacings of 25 mils (0.025 inch). Successive welds in a straight line made in this manner are quite easy to perform using known pulsed laser techniques. On the other hand, making successive welds around a circular interface as shown in FIG. 1 is technically much more difficult. The laser may typically be a neodymium: yttrium-aluminum-garnet (Nd:YAG) pulsed laser having a nominal 50 watt rating that delivers five joules per pulse to each weld site, with each pulse having a duration of five milliseconds. A single pulse gives adequate penetration under these circumstances to give a dependable weld as shown. As is known, a laser pulse delivered by an optical fiber 23 tends to give somewhat deeper penetration than would otherwise be true.

The thinned portions 18 and 19 may be made by using a rotary cutter known in the art as a Woodruff cutter having a typical radius of 0.43 inches. During cutting, the plane of the rotary cutter is parallel to the central axis of sleeve 14, making the thinned regions in the shape of slots as shown in FIG. 3. This reduces the wall thickness of the sleeve 14 typicaly from 0.025 inch to a value typically between 0.010 and 0.014 inch. Forming the thinned regions in this manner is quite convenient since it permits the sleeves 14 to be made of stock material which are then individually cut on opposite sides. Cutting in this manner has been found not to interfere with the ability to mount outer sleeve 14 within the optical coupler for subsequent rotational alignment as was described before.

A particular advantage of the invention as shown in FIGS. 2 and 3 is that it is amenable to mass-production techniques. That is, the thinned portions 18 and 19 can be machined automatically, and three successive welds on opposite sides can be formed automatically on a production line after axial positioning. This is an important consideration because many optical couplers would have to be mass produced in conjunction with any complex optical fiber communication system production program.

The embodiments shown are intended to be merely descriptive of the principles of the inventive concept. While the invention was stimulated by a need to fix optical fiber ferrules to outer sleeves, the disclosed technique may be used in any environment in which laser welding is needed to fix together relatively small parts. Various other embodiments and modifications may be made by those skilled in the art without depending from the spirit and scope of the invention.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US4195980 *May 15, 1978Apr 1, 1980International Standard Electric CorporationFusion sealing
US4263495 *Jul 14, 1978Apr 21, 1981Hitachi, Ltd.Method of splicing optical fibers by CO2 -laser
US4350867 *May 7, 1980Sep 21, 1982Nippon Telegraph & Telephone Public CorporationFusion splicing of multi-layer optical fiber bundles
US4802729 *Jan 7, 1987Feb 7, 1989Loic RivoallanDevice for focusing a light beam and machine for welding optical fibres using this device
JPS61193793A * Title not available
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US5222170 *Aug 17, 1992Jun 22, 1993Bt&D Technologies Ltd.Optical fiber device fabrication
US5268556 *Nov 18, 1992Dec 7, 1993At&T Bell LaboratoriesLaser welding methods
US5273474 *Nov 20, 1992Dec 28, 1993Ngk Spark Plug Co., Ltd.Method of manufacturing a center electrode for a spark plug
US6412304May 22, 2000Jul 2, 2002Stuart J. AdelmanJewelry
US6607304Oct 4, 2000Aug 19, 2003Jds Uniphase Inc.Magnetic clamp for holding ferromagnetic elements during connection thereof
US6804439Sep 9, 2003Oct 12, 2004Yazaki North America, Inc.Method of attaching a fiber optic connector
US6854899 *May 15, 2000Feb 15, 2005Tyco Electronics Amp GmbhFerrule for an optical fiber and process for fastening the ferrule on the optical fiber
US6897404 *Apr 8, 2003May 24, 2005Tyco Electronics Amp GmbhMethod and device for welding contacts to optical waveguides
US6902327Dec 10, 2003Jun 7, 2005Yazaki North America, Inc.Apparatus and method for laser welding a ferrule to a fiber optic cable
US6960027Apr 26, 2000Nov 1, 2005Tyco Electronics Logistics AgMethod of fixing a ferrule to an optical waveguide
US7790999 *Aug 7, 2002Sep 7, 2010Fraunhofer-Gesellschaft Zur Foerderung Der Angewandten Forschung E.V.Laser beam welding method
US7820937 *Oct 27, 2004Oct 26, 2010Boston Scientific Scimed, Inc.Method of applying one or more electromagnetic beams to form a fusion bond on a workpiece such as a medical device
US8696215Mar 13, 2013Apr 15, 2014Corning Cable Systems LlcAdhesive compositions including partially cross-linked resins and coupling agents and methods for use thereof
US8702322Jun 3, 2013Apr 22, 2014Corning Cable Systems LlcOptical connector with adhesive material
US8753021Feb 12, 2013Jun 17, 2014Corning Cable Systems LlcAdhesives for securing optical fibers to ferrules of optical connectors and methods for use thereof
US8755654May 10, 2013Jun 17, 2014Corning Cable Systems LlcCoating removal systems for optical fibers
US8764314Mar 7, 2013Jul 1, 2014Corning Cable Systems LlcOptical fiber and composite inorganic ferrule assemblies and methods
EP1380867A2 *Jul 3, 2003Jan 14, 2004Tyco Electronics AMP GmbHHousing of a connector plug for optical fibres
WO2000067056A1 *Apr 26, 2000Nov 9, 2000Bauer JuergenMethod of fixing a ferrule to an optical waveguide
Classifications
U.S. Classification219/121.64, 385/96, 385/99, 385/98
International ClassificationB23K26/20, G02B6/42, G02B6/38, B23K26/22, B23K26/00
Cooperative ClassificationB23K26/22, G02B6/3874, B23K26/20, G02B6/4248
European ClassificationB23K26/20, B23K26/22, G02B6/42C7, G02B6/38D10A
Legal Events
DateCodeEventDescription
Jan 30, 2001FPAYFee payment
Year of fee payment: 12
Jan 10, 1997FPAYFee payment
Year of fee payment: 8
Dec 21, 1992FPAYFee payment
Year of fee payment: 4
Oct 17, 1988ASAssignment
Owner name: AMERICAN TELEPHONE AND TELEGRAPH COMPANY 550 MADIS
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNORS:COYLE, RICHARD J. JR.;MRACEK, JAROSLAV;REEL/FRAME:004995/0160
Effective date: 19881013